1974 GT 750 loss of power

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Tino996
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Joined: Wed Jan 10, 2018 6:41 pm
Location: gatwick

1974 GT 750 loss of power

Post by Tino996 »

Hi all, I've just about finished the bike rebuild, taken it out for a few rides now, and each time, whilst going uphills and putting more power on, it just seems to die! I have to change down, just to get up the hills!! I have checked the timing. Cleaned, checked the carbs, even installed a new fuel tap in case it was the vacuum diaphgram. Now don't know where to look next? Wondered if anyone else has had this problem/
Thanks, Martyn.
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canaletto5
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Location: Derbyshire

Re: 1974 GT 750 loss of power

Post by canaletto5 »

Hi

What's compression like?

Kev
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PaulD738
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Re: 1974 GT 750 loss of power

Post by PaulD738 »

Check the fuel cap vent isn’t blocked
They're rubbish them Jap bikes lad they won't last five minutes! you want to get yourself a nice Royal Enfield!
A quote from my old dad 8-)

I started out with nothing and I’ve got most of it left!
Tino996
Posts: 19
Joined: Wed Jan 10, 2018 6:41 pm
Location: gatwick

Re: 1974 GT 750 loss of power

Post by Tino996 »

I think the compression is fine, although I don’t have a tester! New pistons and rings fitted. Plugs seem ok in colour.
Tino996
Posts: 19
Joined: Wed Jan 10, 2018 6:41 pm
Location: gatwick

Re: 1974 GT 750 loss of power

Post by Tino996 »

Whilst riding today, I opened fuel cap when going uphill, but didn’t make any difference. So I presume the cap isn’t blocked, but I will check.
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canaletto5
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Re: 1974 GT 750 loss of power

Post by canaletto5 »

Were the barrels re-bored? It might be worth investing in a tester. Kev
Tino996
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Joined: Wed Jan 10, 2018 6:41 pm
Location: gatwick

Re: 1974 GT 750 loss of power

Post by Tino996 »

Barrels were not rebored, I had them checked, but perhaps I should investigate the compression further. What should they be? Thanks, Martyn.
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canaletto5
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Re: 1974 GT 750 loss of power

Post by canaletto5 »

Never less than 95psi. I think around 110psi is the norm for a good engine although it can be as high as 120ish. Check there aren't big variances between the pots (no more than 5psi) Kev
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canaletto5
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Location: Derbyshire

Re: 1974 GT 750 loss of power

Post by canaletto5 »

Also worth checking the exhaust pipes aren't clogged with carbon.
Tino996
Posts: 19
Joined: Wed Jan 10, 2018 6:41 pm
Location: gatwick

Re: 1974 GT 750 loss of power

Post by Tino996 »

Thanks very much, I’ll take a look at those points.
Martyn.
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